Jason Segel has expressed doubt over the believability of his role as Emily Blunt's love interest in Gulliver's Travels.

The Forgetting Sarah Marshall actor, who plays the boyfriend of Blunt's miniature princess in the Jack Black comedy, admitted that becoming a romantic lead was a more daunting prospect than his brutal pre-shoot exercise routine.

He told BANG Showbiz: "Here I needed to be fit. They got me a trainer, which is very different to what I am used to.

Advertisement - Continue Reading Below

"I have hand-to-hand combat, and then I also have to be someone Emily Blunt could be attracted to. In fact, that's been the toughest thing of all."

Segel also spoke of Black's involvement in his casting, adding that he was sincerely grateful for the Tenacious D frontman's endorsement.

"I love Jack. He gave me my first writing job when I was 20 years old on a pilot called 'Black Market Music' that Seth Rogen and I were writing," he said. "Jack fought really hard for me on this movie and I owe him a lot."